Revetment blocks are available in many different shapes and sizes to accommodate different situations to control the erosion of soil. Revetment blocks can be constructed with arms and sockets that interengage together, but are not positively interlocking to prevent lateral separation of neighbor blocks interlocked together. Other revetment blocks have positive interlocking arms and sockets so that when installed in an interlocking manner, the blocks cannot be laterally removed from each other, thereby allowing heavy water flows thereover without dislodging any of the blocks. Such a revetment block is disclosed in U.S. Pat. No. 5,556,228 by Smith.
In order to prevent erosion of the soil in a waterway, revetment blocks are installed as a mat to cover the entire area to be protected from erosion. This often involves lining the bottom and sides of the waterway with revetment blocks so that the water flows over the revetment blocks and the underlying soil is protected from erosion. The particular type of revetment block can be selected based on the velocity and the volume of water that is expected to flow down the waterway. Engineers and hydraulic specialists can determine what style of revetment block is best adapted for these conditions.
Additional conditions taken into consideration is the direction of water flow in the channel or waterway. Since the direction of the flow of water is generally in the same direction, this is usually not a variable that must be considered. However, certain revetment blocks are constructed to control various aspects of the water flow, and thus such blocks must be installed in a certain orientation in order to assure that the water reacts in the proper way when flowing over the blocks. For example, U.S. Pat. No. 8,678,704 by Smith discloses a tapered top revetment block that is installed in a waterway in a certain orientation so that the tapered top tapers upwardly in a downstream direction to reduce the lifting force exerted on the mat of blocks and thus increases the factor of safety. U.S. Pat. No. 8,123,434 by Smith discloses a mat of interlocking revetment blocks where certain blocks of the mat have different heights to thereby form interruptions in the flow of water and create turbulence to slow down the velocity of the water. In other words, by using different height blocks in the mat, the roughness coefficient of the mat is increased, thus slowing down the velocity of the water flowing thereover. The roughness coefficient of a mat of revetment blocks is also known as “Mannings N.”
A field of concern that has not been addressed in terms of water control is that of wave surges during times when higher than usual waves surge over areas that are usually not protected from erosion. For example, wave surges can be experienced during hurricanes, tidal waves, tsunamis, etc., where the surges of waves flow over dams, levees and the like. The hurricane Katrina hit the New Orleans area and breached many of the levees to the extent that the levees no longer protected the land side. Since the landside of the levees generally did not experience water flow, there was often no protection on such side of the levee, except that which was necessary to prevent erosion of the levee during heavy rainfalls. Often the river side of the levee was protected from erosion as that side of the levee experiences water flow in the downstream direction during flooding of the river.
When a levee experiences a storm surge, the waves can be sufficiently high as to flow over the levee and erode the backside of the levee, thereby reducing its strength and integrity. The wave surges are often caused by high winds. If the erosion on the backside of the levee continues, the levee can be breached so that water flow in either direction through the hole in the levee is possible, and flooding of the land side of the levee can occur. Moreover, as the wave surge flows over the levee, it speeds up as it flows down the incline on the land side of the levee, thereby accelerating soil erosion on the backside of the levee.
From the foregoing, it can be seen that a need exists for a technique to protect levees, and the like, from storm surges not only on the front side, but also on the backside or land side of the levee. A further need exists for a method of installing revetment blocks on the land side of a levee to slow down the velocity and energy of water and reduce the kinetic energy thereof as a wave surges over the levee. Another need exists for a method of protecting the land side of levees from erosion as well as controlling the energy of water flowing down the land side of the levee to reduce the destructive force of the water.